Changes in UDPG: Sterol glucosyltransferase activity in Calendula officinalis

UDPG: sterol glucosyltransferase and acyltransferase which catalyse acylation of steryl glucosides are active in leaves, roots and flowers during the whole vegetative period of Calendula officinalis. The high activity of glucosyltransferase in young, developing tissues and its subsequent rapid decrease in activity in mature organs suggests that steryl glucosides are involved in the formation of some cell structures rather than in sterol transport as such within the plant.     

Osmotic adjustment in leaves of sorghum in response to water deficits

The relationships among the total water potential, osmotic potential, turgor potential, and relative water content were determined for leaves of sorghum (Sorghum bicolor [L.] Moench cvs. `RS 610' and `Shallu') with three different histories of water stress. Plants were adequately watered (control), or the soil was allowed to dry slowly until the predawn leaf water potential reached either −0.4 megapascal (MPa) (treatment A) or −1.6 MPa (treatment B). Severe soil and plant water deficits developed sooner after cessation of watering in `Shallu' than in `RS 610', but no significant differences in osmotic adjustment or tissue water relations were observed between the two cultivars. In both cultivars, the stress treatments altered the relationship between leaf water potential and relative water content, resulting in the previously stressed plants maintaining higher tissue water contents than control plants at the same leaf water potential. The osmotic potential at full turgor in the control sorghum was −0.7 MPa: stress pretreatment significantly lowered the osmotic potential to −1.1 and −1.6 MPa in stress treatments A and B, respectively. As a result of this osmotic adjustment, leaf turgor potentials at a given value of leaf water potential exceeded those of the control plants by 0.15 to 0.30 MPa in treatment A and by 0.5 to 0.65 MPa in treatment B. However, zero turgor potential occurred at approximately the same value of relative water content (94%) irrespective of previous stress history. From the relationship between turgor potential and relative water content there was an approximate doubling of the volumetric elastic modulus, i.e. a halving of tissue elasticity, as a result of stress preconditioning. The influence of stress preconditioning on the moisture release curve is discussed.     

Free sterols,steryl esters,glucosides, acylated glucosides and water-soluble complexes in Calendula officinalis

In 3- and 14-day-old seedlings and in the leaves of Calendula officinalis the following sterols were identified: cholestanol, campestanol, stigmastanol, cholest-7-en-3-β-ol, 24-methylcholest-7-en-3β-ol, stigmast-7-en-3β-ol, cholesterol, campesterol, sitosterol, 24-methylcholesta-5,22-dien-3β-ol, 24-methylenecholesterol, stigmasterol and clerosterol. Sitosterol was predominant in young and stigmasterol in old tissues. Young tissues contained relatively more campesterol but in old tissues a C₂₈Δ^5,22 diene was present suggesting transformation of campesterol to its Δ^5,22 analog, similar to that of sitosterol to stigmasterol. All the identified sterols were present as free compounds and also in the steryl esters, glucosides, acylated glucosides and water-soluble complexes. The variations in the amounts of these fractions in the embryo axes and cotyledons of 3- and 14-day-old seedlings and the distribution of individual sterols among the fractions are discussed.     

Sterol conjugate interconversions during germination of white mustard (Sinapis alba)

Changes in the content of free sterols (FS), steryl esters (SE), steryl glucosides (SG) and acylated steryl glucosides (ASG) in germinating seeds of white mustard (Sinapis alba) were studied together with parrallel changes in specific activities of some enzymes involved in sterol conjugate transformation. It has been found that a distinct increase in the net SE content and a similar, but less pronounced, increase in SG content at the beginning of germination can be correlated with a distinctly earlier appearance of SE and SG synthesizing enzymes, i.e. triacylglycerol: sterol acyltransferase and UDPG: sterol glucosyltransferase in comparison with hydrolytic activities, i.e. SE hydrolase and SG hydrolase. Our results suggest that metabolism of SG and ASG takes place mainly in the cotyledons while SE metabolism takes place mainly in the roots.     

Physiological function of water channels as affected by salinity in roots of paprika pepper

The sap flow (Jv) and the osmotic pressure-dependent hydraulic conductance (L₀) of detached exuding root systems from paprika pepper plants (cv. Albar) were measured. Plants stressed with NaCl (30 m M ) and with six times the macronutrients of the Hoagland nutrient solution (6×HNS) were compared with controls grown in complete Hoagland nutrient solution. Jv of +NaCl and +6×HNS plants decreased markedly, but recovered to values similar to those of controls after removal of the treatments. Hydraulic conductance L₀ was always less in NaCl plants than in controls and 6×HNS. A total increase in the ion concentration of the xylem (except Na⁺ and Cl⁻) was observed with both treatments. In control and 6×HNS plants, HgCl₂ treatment (50 μ M ) caused a sharp decline in L₀ to values similar to those of NaCl-stressed roots, but were restored by treating with 5 m M dithiothreitol (DTT). However, in NaCl roots only a slight effect of Hg²⁺ and DTT was observed. In each treatment, there was no difference in the flux of K⁺ into the xylem after HgCl₂ and DTT application. The results suggest that NaCl decreased L₀ of the roots by reducing either the activity or abundance of Hg-sensitive water channels. The putative reduction in water-channel function of NaCl-treated plants did not seem to be due to the osmotic effect.     

The incorporation of mevalonate-[2-14C] into the sterol fractions of Calendula officinalis

The incorporation of mevalonate-[2-¹⁴C] into the free sterols, steryl esters, steryl glucosides, acylated steryl glucosides and water-soluble complexes was investigated and the sterols of each fraction were separated into stanols, Δ⁷ sterols, Δ⁵ sterols, stigmasterol, clerosterol and methylene-cholesterol. The stanols and Δ⁷ sterols were more strongly labelled in the steryl esters than in the free sterols. The Δ⁵ sterols and stigmasterol were more intensively labelled in the free sterols than in the steryl esters. All sterol types were more labelled in the steryl glycosides than in the acylated steryl glucosides. Stanols were probably formed from Δ⁷ or Δ⁵ precursors.     

Phytosterols in tobacco leaves at various stages of physiological maturity

Leaves of varying maturity from 84-day-old tobacco plants were harvested and analyzed for total sterol and their individual sterol components. The mature leaves had a significant higher sterol content than the immature leaves. Separation into free sterols, steryl esters, steryl glycosides, and acylated steryl glycosides showed that the free sterols accounted for most of the sterol increase, and stimgasterol was principally responsible for this increase.     

Sterol Composition of the Corn Cyst Nematode,Heterodera zeae,and Corn Roots

Sterols from free sterol and steryl ester fractions from Heterodera zeae and from total lipids of Zea mays roots were analyzed by gas-liquid chromatography (GLC) and by GLC-mass spectrometry. The major free sterols of H. zeae were 24-ethylcholesterol (54.4% of total free sterol), 24-ethylcholesta-5,22-dien-3β-ol (13.3%), 24-methylcholesterol (12.5%), and cholesterol (7.2%). The same four sterols comprised 34.6%, 7.2%, 30.3%, and 18.6%, respectively, of the esterified sterols of H. zeae. Corn root sterols included 46.6% 24-ethylcholesta-5,22-dien-3β-ol, 16.7% methylcholesterol, 16.4% cycloartenol, 12.7% 24-ethylcholesterol, and 0.5% cholesterol. The sterol 24-composition of H. zeae differed greatly from that of the only other cyst nematode previously investigated, Globodera solanacearum.     

Steryl glycosides and acyl steryl glycosides from Musa paradisiaca

From peeled fruits of Musa paradisiaca (banana, vegetable variety), two new acyl steryl glycosides, sitoindoside-III and sitoindoside-IV, and two new steryl glycosides, sitosterol gentiobioside and sitosterol myo-inosityl-β-D-glucoside, have been isolated by gradient solvent extraction and extensive chromatography (CC, prep. TLC, GC and HPLC). The compounds have been characterized by comprehensive spectroscopic analyses (IR, ¹H NMR, GC, mass spectra, [α]_D) and crucial chemical transformation. Additionally, seasonal variations of the total sterols, free sterols, steryl esters, steryl glycosides and acyl steryl glycosides in the active samples of banana have been analysed. The results provide a basis for the observed fluctuations in the anti-ulcerogenic activity of the extracts, in different seasons, and the importance of appropriate formulation of the pure principles to optimize the activity.     

Short episodes of water stress increase barley root resistance to radial shrinkage in a dehydrating environment

Although plant shoots can be 'hardened' by abiotic stresses, little is known about such changes in roots. In order to investigate possible induction of root-hardening in response to short water-stress episodes, barley seedlings ( Hordeum vulgare L) hydroponically grown under a controlled environment were moderately water-stressed by addition of a non-penetrating osmoticum, polyethylene glycol (PEG) 6000 at −0.4 MPa water potential, to the aerated nutrient solution. Seedlings were then hydrated in dilute nutrient solution without PEG before excision and assay of the seminal roots. Previous water stress treatments for 72 h, 12 h, or even 6 h induced an apparent root-hardening process. Thus, root radial shrinkage during subsequent exposure to strongly dehydrating conditions was remarkably decreased. The root hardening was related to biophysical adjustments: turgor-pressure increased while osmotic potential decreased from −0.45 ± 0.02 MPa to −0.60 ± 0.02 MPa. Moreover, the maximum bulk volumetric modulus of elasticity, ɛ_max determined by pressure–volume analysis, increased from 2.1 ± 0.4 MPa to 3.7 ± 0.4 MPa, i.e. root elasticity was decreased. Root hardening in response to episodes of water stress may have ecological significance for barley plants in regions where intermittent drought episodes are frequent.     

A ca. 40 kDa maize (Zea mays L.) embryo dehydrin is encoded by the dhn2 locus on chromosome 9

Dehydrins (LEA D11 proteins) are the products of multigene families in a number of higher plants [5]. To date, however, only one dehydrin locus, dhn1 (a major embryo and drought-induced protein of ca. 18 kDa) has been placed on chromosome 6L of the genetic linkage map of maize. The presence of a larger, ca. 40 kDa embryo protein that is also specifically detected by anti-dehydrin antibodies had been observed in some maize inbreds, including B73, suggesting that other dhn loci may exist. The ca. 22 kDa and ca. 40 kDa immunopositive proteins were purified from B73 and their amino acid compositions determined. The two proteins' amino acid compositions are typical of dehydrins, yet they differ from each other, indicating that they are distinct dhn gene products. Different size alleles for both proteins, or presence/absence in the case of the ca. 40 kDa protein, were evident from comparisons of embryo proteins of various maize inbreds. Analysis of segregating F₂ progeny derived from self-pollination of F₁ hybrids from four crosses (B73 × OH43, Mo17 × A632, AHO × A632, Latente × A632) revealed that alleles of the two genes assort independently. Map positions of the two dhn loci were then determined using two maize recombinant inbred line (RIL) mapping populations. The predicted map position of the gene controlling production of the ca. 22 kDa protein confirmed that this protein is the product of the dhn1 gene. The gene encoding the ca. 40 kDa dehydrin-like protein maps to a new locus on chromosome 9S near wx1, which we have named dhn2.     

Maize lateral root developmental plasticity induced by mild water stress. I: Genotypic variation across a high‐resolution series of water potentials

Lateral root developmental plasticity induced by mild water stress was examined across a high‐resolution series of growth media water potentials (Ψ_w) in two genotypes of maize. The suitability of several media for imposing near‐stable Ψ_w treatments on transpiring plants over prolonged growth periods was assessed. Genotypic differences specific to responses of lateral root growth from the primary root system occurred between cultivars FR697 and B73 over a narrow series of water stress treatments ranging in Ψ_w from ?0.25 to ?0.40 MPa. In FR697, both the average length and number of first‐order lateral roots were substantially enhanced at a Ψ_w of ?0.25 MPa compared with well‐watered controls. These effects were separated spatially, occurring primarily in the upper and lower regions of the axial root, respectively. Furthermore, first‐order lateral roots progressively increased in diameter with increasing water stress, resulting in a maximum 2.3‐fold increase in root volume at a Ψ_w of ?0.40 MPa. In B73, in contrast, the length, diameter, nor number of lateral roots was increased in any of the water stress treatments. The genotype‐specific responses observed over this narrow range of Ψ_w demonstrate the necessity of high‐resolution studies at mild stress levels for characterization of lateral root developmental plasticity.     

Differential Senescence of Maize Hybrids following Ear Removal : I. Whole Plant

Visual senescence symptoms and associated changes in constituent contents of three field-grown maize (Zea mays L.) hybrids (Pioneer brand 3382, B73 × Mo17, and Farm Service brand 854) were compared in response to ear removal. Whole plants were harvested at eight intervals during the grain-filling period, and analyzed for dry matter, total N and nitrate N, phosphorus, sugars, and starch.

Upper leaves of earless P3382 and B73 × Mo17 showed reddish discoloration by 25 days after anthesis (DAA) and all leaves had lost most of their chlorophyll by 40 DAA. In striking contrast, leaves of earless FS854 plants remained green and similar in appearance to eared controls throughout the grain-filling period.

For all hybrids, ear removal led to a decrease in dry weight, reduced N, total N, and phosphorus contents of the total plant, and an increase in carbohydrate content of the leaves and stalks, relative to respective controls. Although changes in carbohydrate and N contents, which previously had been associated with senescence, were observed for all earless hybrids, these changes were followed by accelerated senescence and early death only for P3382 and B73 × Mo17. By 30 DAA, earless P3382 and B73 × Mo17 plants ceased to accumulate dry weight, total N, and phosphorus, indicating a termination of major metabolic activities. In contrast, earless FS854 plants retained a portion of these metabolic activities until 58 DAA, indicating a role for roots in determining rate of senescence development. Thus, the course of senescence was more accurately reflected by measurements of metabolic activities than by measurements of metabolite contents at any given time. These results show that the ear per se does not dictate the rate or completion of the senescence process, and implicated an association between the continued accumulation of N and associated root activities with the delayed senescence pattern of the earless FS854 plants. It is evident that studies involving control of senescence among species must also consider genotypic influences within species.

     

The production of callus capable of plant regeneration from immature embryos of numerous Zea mays genotypes

In the summer of 1983, immature embryos from 101 selfed inbred lines and germplasm stocks of Zea mays L. were examined for their ability to produce callus cultures capable of plant regeneration (regenerable cultures) using a medium with which some limited success had previously been obtained. Forty-nine of the genotypes (49%) produced callus which visually appeared similar to callus previously cultured and shown to be capable of plant regeneration. After five months, 38 of these genotypes were alive in culture and plants were subsequently regenerated from 35 (92%) of them. No correlation was observed between plant regeneration and callus growth rate, the vivipary mutation (genes vp1, 2, 5, 7, 8 and 9), or published vigor ratings based on K⁺ uptake by roots. When F₁ hybrid embryos were cultured, 97% of the hybrids having at least one regenerable parent also produced callus capable of plant regeneration. No regenerable cultures were obtained from any hybrid lacking a parent capable of producing a regenerable callus culture.In the summer of 1984, immature embryos from 218 additional inbred lines and germplasm stocks were plated and examined for their ability to produce regenerable callus cultures on media containing altered micronutrient concentrations, 3,6-dichloro-o-anisic acid (dicamba), glucose, and elevated levels of vitamin-free casamino acids and thiamine. Of these genotypes 199 (91%) produced callus that was regenerable in appearance. In the 1984 study, plant regeneration was noted in many commercially important inbreds, including B73, Mo17, B84, A632, A634, Ms71, W117, H99³H95 and Cm105. Thus tissue-culture techniques are now available to obtain callus cultures capable of plant regeneration from immature embryos of most maize genotypes.Abbreviations trade names 2,4-D 2,4-dichlorophenoxyacetic acid - dicamba 3,6-dichloro-o-anisic acid     

Genotypic variation in tissue water relations of leaves and roots of black walnut (Juglans nigra) seedlings

Genetic variation in the drought response of leaf and root tissue water relations of seedlings of eight sources of black walnut ( Juglans nigra L.) was investigated using the pressure-volume technique. Tissue water relations were characterized at three stages of a drying cycle during which well-watered plants were allowed to desiccate and then were reirrigated.
Sources varied both in the capacity for and degree of leaf and root osmotic adjustment, and in the mechanism by which it was achieved. A decrease in osmotic potential at the turgor loss point (ψ_πp) of 0.4 MPa was attributable to increased leaf tissue elasticity in seedlings of four sources, while seedlings of an Ontario source exhibited a 0.7–0.8 MPa decline in ψ_πp as a result of both increased solute content and increased leaf tissue elasticity. Seedlings of a New York source showed no detectable osmotic adjustment.
In roots, decreased ψ_πp (osmotic potential at full hydration) and ψ_πp were observed under drought. Sources that exhibited significant leaf osmotic adjustment also generally showed a similar response in roots. Tissue elasticity and ψ_πp of roots were higher than those of shoots, whereas ψ_πp of the two organs was similar for most sources. Because of greater elasticity, roots exhibited a more gradual decline in turgor and total water potential than did leaves as tissue relative water content decreased.     

The glass transition behavior of the globular protein bovine serum albumin

The glass-like transition behavior of concentrated aqueous solutions of bovine serum albumin was examined using rheological techniques. At mass fractions >0.4, there was a marked concentration dependence of viscosity with a glass-like kinetic arrest observed at mass fractions in the region of 0.55. At mass fractions >0.6 the material behaved as a solid with a Young's modulus rising from approximately 20 MPa at a mass fraction of 0.62-1.1 GPa at 0.86. The solid was viscoelastic and exhibited stress relaxation with relaxation times increasing from 33 to 610 s over the same concentration range. The concentration dependence of the osmotic pressure was measured, at intermediate concentrations, using an osmotic stress technique and could be described using a hard sphere model, indicating that the intermolecular interactions were predominantly repulsive. In summary, a major structural relaxation results from the collective motion of the globules at the supra-globule length scale and, at 20 degrees C, this is arrested at water contents of 40% w/w. This appears to be analogous to the glass transition in colloidal hard spheres.     

Sterols in relation to ageing of seeds of Helianthus annuus and Cicer arietinum

Under accelerated ageing at high relative humidity and high temperature for 4 days germination and membrane permeability remained unaffected both in sunflower and chick pea seeds. However, the steryl glycoside concentration in the pooled leachate increased progressively with ageing. Total sterols, as well as steryl glycosides and free sterols of the seeds, increased with a concomitant decline in steryl esters under accelerated ageing. Pretreatment with the sterol biosynthesis inhibitor SK & F 7997A₃ prevented the increase of total sterols under accelerated ageing conditions but there were increases in the amounts of steryl glycosides and free sterols and a decrease in steryl ester after such treatment, therefore, indicating interconversions of the various sterol types. Accelerated ageing also caused increases in free amino acids and soluble carbohydrate. Low relative humidity-high temperature and high relative humidity-low temperature failed to produce such effects.     

Differential Senescence of Maize Hybrids following Ear Removal : II. Selected Leaf

In conjunction with a study of the effects of ear removal on the senescence of whole maize (Zea mays L.) plants, visual symptoms and associated changes in constituent contents and activities of a selected leaf (first leaf above the ear) were determined. Leaves were sampled from field-grown eared and earless Pioneer brand 3382, B73 × Mo17, and Farm Services brand 854 maize hybrids at nine times during the grainfilling period.

Visual symptoms indicated the following sequence and rate of senescence: earless B73 × Mo17 > earless P3382 » eared B73 × Mo17 » eared P3382 ≤ earless FS854 > eared FS854. All earless hybrids showed increases in leaf dry weight and sugar content; however, the increases were transitory for P3382 and B73 × Mo17, but continuous throughout the grain-filling period for FS854, indicative of continued photosynthetic activity of the latter. All earless hybrids exhibited similar and transitory starch accumulation patterns. Thus, FS854 was an exception to the concept that carbohydrate accumulation accelerates leaf senescence. Ear removal resulted in accelerated losses of reduced N, phosphoenolpyruvate and ribulose bisphosphate carboxylases, phosphorus, chlorophyll, nitrate reductase activity, and moisture for P3382 and B73 × Mo17 plants. In contrast, the loss of all components (except phosphorus) was similar for the selected leaf of earless and eared FS854.

Although the loss of nitrate reductase activity, reduced N, and carboxylating enzymes accurately reflected the development of senescence of the selected leaf, the rate of net loss of reduced N and carboxylating enzymes appeared to be regulated. We deduced that the rate of flux of N into the leaf was a factor in regulating the differing rates of senescence observed for the six treatments; however, we cannot rule out the possibility of concurrent influence of growth regulators or other metabolites.

     

Occurrence of steryl glycosides and acylated steryl glycosides in some marine algae

There is some controversy concerning the presence of steryl glycosides and acylated steryl glycosides in eucaryotic algae. These two classes of sterol compounds were investigated in species belonging to the three major groups of eucaryotic algae: green algae (Ulva gigantea, Cladophora rupestris), brown algae (Fucus vesiculosus, Ascophyllum nodosum), and red algae (Rhodymenia palmata, Porphyridium sp.). All these algae contain both steryl glycosides and acylated steryl glycosides. The sterol components of these compounds vary according to the alga but they are always the same as the free sterols of the alga in question. The most common sugar moiety is glucose. In the acylated steryl glycosides, the fatty acid is mainly palmitic acid. The percentage of these compounds (as a percentage of the total sterol content) is often low.     

Steryl chlorin esters in sediments of the southern Baltic Sea

Sediments of the southern Baltic Sea were analysed for content of steryl chlorin esters, the chlorin compounds discovered recently in the marine environment. The chlorin esters occur in the Baltic sediments in substantial amounts and form a considerable fraction of the total chlorin content. Among the physicochemical parameters studied the highest correlation with the steryl chlorins showed organic carbon content in sediments and the content of fraction of sediments smaller than 10 μm. A significant correlation was observed between the steryl chlorins content and other chlorins as chlorophylla, phaeophytina, pyrophaeophytina as well as with β-carotene, the distinctly less significant correlation was with phaeophorbidea. This indicates an other way of formation of the steryl chlorins from algae than zooplankton grazing.